Transmission element for the transmission of power and/or torques, oscillation damper and method for oscillation damping

ABSTRACT

A transmission element assembly for transmitting forces and/or torques, the assembly including a transmission element, a component in effective connection with the transmission element so that the transmission element is asymmetrically excitable into oscillations by the component, and an oscillation damper which is of asymmetrical design and is in effective connection with the transmission element.

PRIORITY CLAIM

This is a U.S. national stage of application No. PCT/EP99/02718, filedon Apr. 22, 1999. Priority is claimed on that application and on thefollowing application:

Country: Germany, Application No.: 198 21 165.1, Filed: May 12, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a transmission element for the transmission offorces and/or torques, in particular for motor vehicles, having anoscillation damper, and to a method for damping oscillations.

2. Description of the Prior Art

Transmission elements are known in an extremely wide range ofembodiments and applications. These transmission elements are used totransmit forces and/or torques from one location to another.

In a motor vehicle, for instance, forces and torques are transmitted vialinkages or other transmission elements for the purpose of controllingand regulating sequences of motion. The torque produced by the driver atthe steering wheel for the purpose of steering the vehicle, for example,is transmitted to the steering gear by a steering column.

Due to a wide range of different factors, there is the risk that thetransmission element will be excited into oscillations. Theseoscillations are generally unwanted and impair comfort.

The use of an oscillation damper for reducing and/or absorbingoscillations is known.

German reference DE 37 061 35 A1, for instance, proposes to suppressunwanted axial oscillations of a compensating coupling of an injectionpump drive by means of a damping device. The damping device essentiallycomprises an elastomeric compound, which is arranged within a hollowshaft and embedded in the center of which is a bolt.

German reference DE 197 26 293, which is a later publication, disclosesthe fact that bending oscillations of a drive or cardan shaft designedas a hollow shaft can be reduced in an effective manner if anoscillation damper is arranged within the hollow shaft at the point ofmaximum oscillation. The oscillation damper has a damper mass and anelastic coupling element.

SUMMARY OF THE INVENTION

The problem underlying the present invention is to provide atransmission element and a oscillation damper that have a wider area ofapplication relative to the prior art. The intention is furthermore toprovide a method for damping oscillations.

Pursuant to these objects, one aspect of the present invention residesin a transmission element having a component which is in effectiveconnection with the transmission element. The effective connection canbe established by means of a form-locking and/or force-lockingconnection.

Due to the component, the transmission element can be excited intoasymmetrical oscillations.

Fundamentally, oscillations occur in various modes. A rigid body whichis elastically suspended can be excited into longitudinal oscillationsand rotary oscillations, and an elastic body can additionally be excitedinto bending oscillations and torsional oscillations. A furtherdistinction is drawn between symmetrical and asymmetrical oscillations.In the case of symmetrical oscillations, the oscillatory motion takesplace symmetrically with respect to a reference axis of the body. Incontrast, asymmetrical oscillations have different amplitudes andfrequencies in relation to the reference axis of the body.

The present invention is concerned with asymmetrical oscillations andtheir damping and absorption on transmission elements. A longitudinalaxis of the transmission element is used as a reference axis.

It is self-evident that damping and absorption of oscillations includesany reduction in the amplitudes of motion and the associated effectiveforces.

To damp the asymmetrical oscillation of the transmission element, anoscillation damper is provided which has asymmetrical dampingcharacteristics, which is in effective connection with the transmissionelement. By virtue of the design of the oscillation damper, asymmetricaldamping properties are achieved, ensuring more effective damping of theasymmetrical oscillations which occur than would be the case with asymmetrical oscillation damper.

The oscillation damper is generally arranged as close as possible to theantinode, i.e. the location of maximum oscillation amplitude, since thisis generally the best location for effective oscillation damping.

Asymmetrical oscillations frequently occur at motor-vehicle steeringcolumns, for example. Due to the integration of other components, e.g.airbags and electrical switch elements, and the need to ensure a clearview of the instruments, steering wheels are generally of asymmetricalconstruction. Since a vehicle predominantly travels straight ahead, thesteering wheel as a component is preferably in a central position. Inthis position, the steering column as a transmission element is excitedinto different oscillations transversely to the longitudinal axis of thevehicle to those perpendicular thereto as regards the mode and frequencyof oscillation.

The oscillation damper can be arranged in the region of an outer wall ofthe transmission element, thereby making it to easy to fit and to checkfor adjustment and damage.

If a hollow transmission element is used, it is also possible for theoscillation damper to be arranged within the transmission element. Thisarrangement saves space and protects the oscillation damper from damageand loss of correct adjustment.

The type of arrangement that is ultimately selected depends on theparticular circumstances of the application.

It is also possible to provide a plurality of oscillation dampers onand/or in the transmission element. This is appropriate, in particular,if, for example, a relatively long transmission rod is excited intodifferent modes of oscillation, i.e. there is a plurality of locationsof maximum oscillation amplitude. In this case, it is advantageous tofix an appropriately designed oscillation damper at each antinode, i.e.an oscillation damper that is tuned to the respective frequency.

The oscillation damper can have a damper mass and an elastic couplingelement, manufactured from elastomeric plastic for example. Theeffective connection between the oscillation damper and the transmissionelement is effected via the elastic coupling element.

The elastic coupling element can be of an appropriate design in order toobtain the desired asymmetrical damping properties in the oscillationdamper. For this purpose, the elastic coupling element is of moremassive construction on a preferred transverse axis than on a transverseaxis perpendicular to the preferred transverse axis, it being possibleto achieve this, for example, by means of holes, cavities or the absenceof material entirely. In the preferred transverse axis, on which theelastic coupling element is massively arranged, there is a greaterstiffness, with the result that, in this direction, the oscillationdamper has a higher natural frequency. In contrast to this, the elasticcoupling element is of more flexible construction, i.e. less stiff,perpendicularly to the preferred transverse axis or in anotherdirection, with the result that the oscillation damper has a lowernatural frequency in this direction. The natural frequency of theoscillation damper in each case determines the frequency range in whichit damps oscillations occurring in the component connected to it, inthis case the transmission element.

If a hollow shaft is used as a transmission element, a sleeve can bearranged between the hollow transmission element and the elasticcoupling element of the oscillation damper. The sleeve can be producedcheaply, protects the elastic coupling element from damage duringassembly and makes assembly easier.

The damper mass of the oscillation damper can be covered with elasticmaterial, e.g. rubber. The elastic covering damps impact noises that canoccur if the damper mass unintentionally makes contact with thetransmission element. Moreover, the elastic covering protects both thedamper mass and the transmission element from mechanical damage andcorrosion.

The elastic covering of the damper mass can also be in the form ofprojecting knobs. Impact noises are thereby damped even more effectivelythan with a uniform covering, owing to greater flexibility.

The transmission element can have an adjusting device associated withit. This can be arranged on the transmission element and/or on theoscillation damper. This ensures that the oscillation damper can bemounted securely in the desired position and with the desiredorientation on or in the transmission element and remains there. If ahollow shaft is used, adjustment can be accomplished by means of alongitudinal slot in the sleeve of the oscillation damper and by meansof a web or pin in the hollow shaft.

Other adjusting devices are possible and known to the person skilled inthe art.

The oscillation damper is distinguished by the fact that the couplingelement has asymmetrical elastic properties in a plane of action. Theoscillation damper has a damper mass and an elastic coupling elementconnected to it, the coupling element having asymmetrical elasticproperties in a plane of action. The coupling element is generallyconnected effectively both to the damper mass itself and to a component,e.g. a transmission element, which is excited asymmetrically intounwanted oscillations. The effective connection can in each case beestablished by means of a form-locking and/or force-locking connection.

The asymmetrical elastic properties of the coupling element can bebrought about by shaping. The oscillation damper can, for instance, beprovided with a shaped elastic coupling element made from a homogeneousmaterial. In this case, the desired asymmetrical damping properties ofthe oscillation damper are obtained from the fact that, in onedirection, in a plane perpendicular to the longitudinal axis of theoscillation damper, the coupling element has a different stiffness thanin another direction, e.g. a transverse direction.

However, the oscillation damper can also be provided with an elasticcoupling element in which different materials, each with differentproperties, are combined asymmetrically. In this case, the desiredasymmetrical damping properties of the oscillation damper are achievedby virtue of the fact that the asymmetrically designed stiffness of theelastic coupling element is brought about by the differences in theproperties, in particular by the differences in stiffness, of thematerials combined in it.

It is also conceivable for the elastic coupling element of theoscillation damper to be of asymmetrical design both through shaping andthrough the combination of different materials and for the desiredasymmetrical damping properties of the oscillation damper to be achievedin this way.

The method for damping oscillations, in particular oscillations of atransmission element, is distinguished by the fact that the dampingtakes place in different directions in a plane of action, with adifferent damping stiffness in each case. This results in asymmetricaldamping which, as already explained above, leads to good results incertain cases.

The invention is explained in greater detail below by way of examplewith reference to a steering column of a motor vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawing, in each case in schematic representation:

FIG. 1 shows a side view of a transmission element;

FIGS. 2 and 2A show a longitudinal section through an oscillationdamper;

FIG. 3 shows a cross section through an oscillation damper; and

FIG. 4 shows a view similar to FIG. 1 with two dampers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a transmission element 1, which is designed as a steeringcolumn and has a first, hollow steering rod 2, a universal joint 3 and asecond steering rod 4. The transmission element 1 transmits the rotarymotion T of a steering wheel 5 to a steering gear 6. Close to thesteering wheel 5, the steering rod 2 is arranged rotatably in a bearing7. Vibration and shocks F that occur in the vehicle excite the steeringrod 2 to perform bending oscillations. Since the frequencies and modesof oscillation that are excited perpendicular to the plane of thedrawing are different to those excited in the plane of the drawing,oscillations that are asymmetrical with respect to the longitudinal axisZ of the steering rod 2 occur in the steering rod 2. This asymmetry isintensified by the asymmetrical design of the steering column'sstiffness.

An oscillation damper 8 is arranged at a suitable location within thehollow steering rod 2 to damp the asymmetrical oscillations. As shown inFIG. 2, this oscillation damper 8 essentially comprises a damper mass 9,which is of compact construction and, in the center, has a neck. At thisneck, the damper mass 9 is connected to an elastic coupling element 10.The elastic coupling element 10 is surrounded by a sleeve 11, by meansof which the oscillation damper 8 is connected to the transmissionelement 2, thus establishing an effective connection.

FIG. 2A shows an adjusting device 23 formed as a pin in the steering rod2.

As shown in cross section in FIG. 3, the elastic coupling element 10 isof a design with respect to a longitudinal axis Z so as to provideasymmetrical damping characteristics. Along one axis Y (firsttransversal direction) of the plane of action P, the elastic couplingelement 10 has solid and hence rigid characteristics while,perpendicular to this (along the X axis in a second transversaldirection), it has more flexible and hence softer characteristics owingto the absence of material. In the direction of the axis Y in which itis of stiff construction, the oscillation damper 8 damps a highfrequency while, in the direction of the axis X in which it is of softconstruction, it damps a low frequency. The oscillation damper 8 thushas asymmetrical damping properties.

FIG. 3 furthermore illustrates knobs 12, with which the damper mass 9 iscovered and which can be composed of rubber, for example. By means ofthis covering, impact noises are damped and damage is avoided, somethingthat can occur if the damper mass 9 unintentionally makes contact withthe steering rod 2 in certain modes of oscillation.

FIG. 4 shows an embodiment having two oscillation dampers 8, 8′.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

What is claimed is:
 1. A transmission element assembly for transmissionof forces and/or torques in a motor vehicle, comprising: a vehiclecomponents; a transmission element that transmits forces and/or torquesfrom one location on the transmission element to another location on thetransmission element and is in effective connection with the vehiclecomponent so that the transmission element is asymmetrically excitableby the vehicle component into oscillations of different amplitudes andfrequencies in relation to a reference axis of the transmission element;and an oscillation damper which is in effective connection with thetransmission element, is located between the two locations, and has adamper mass and an elastic coupling element arranged between the dampermass and the transmission element, the elastic coupling element havingasymmetrical damping characteristics so as to provide a higher dampingstiffness in a first transversal direction perpendicular to thereference axis than in a second transversal direction and the referenceaxis.
 2. The transmission element assembly as defined in claim 1,wherein the oscillation damper is arranged within the transmissionelement.
 3. A transmission element as defined in claim 1, wherein aplurality of oscillation dampers are provided.
 4. A transmission elementassembly as defined in claims 1, wherein the coupling element has anasymmetrical construction.
 5. A transmission element assembly as definedin claim 1, and further comprising a sleeve-arranged between thetransmission element and the elastic coupling element of the oscillationdamper.
 6. A transmission element assembly as defined in claim 1,wherein the damper mass of the oscillation damper is covered withelastic material.
 7. A transmission element assembly as defined in claim6, wherein the elastic material is knob-shaped.
 8. A transmissionelement assembly as defined in claim 1, and further comprising anadjusting device associated with the transmission element.